1. Field of the Invention
This invention relates to a halogenated resin composition which is stabilized by adding thereto a specific stabilizer system. More particularly, it relates to a halogenated resin composition whose heat stability, weatherability, initial coloration, thermal coloration and adhesiveness are improved by adding thereto an overbased alkaline earth metal carboxylate/carbonate together with a .beta.-diketone compound or a metal salt thereof.
2. Description of the Prior Art
It is known that a halogenated resin, which is less stable to heat and light, would frequently undergo decomposition mainly caused by dehydrohalogenation in a thermal molding step or when used at a relatively high temperature or upon exposure to ultraviolet rays, for example, outdoor usage.
Thus attempts have been made to improve the stability of a halogenated resin by adding several heat stabilizers such as metal salts of organic acids, inorganic basic metal compounds, organotin compounds, organic phosphite compounds, epoxy compounds or .beta.-diketone compounds thereto.
Among these heat stabilizers, metal salts of organic acids have been used as a fundamental stabilizer for halogenated resins. Further, there has been already proposed the use of a metal salt of an organic acid, wherein a metal base is used in a stoichiometrically excessive amount (i.e., so-called "overbased complex"), as described in, for example, Japanese Patent Publication No. 49019/1977.
Although these stabilizers comprising metal salts of organic acids are effective in the improvement of the heat stability over a prolonged period of time, they are disadvantageous from the viewpoint of coloration, in particular, coloration in the initial stage of heating or after the completion of heating.
It is further known that .beta.-diketone compounds are stabilizers which can mainly improve coloration. There has been proposed in, for example, Japanese Patent Publication No. 8786/1967, Japanese Patent Laid-Open No. 34939/1976, Japanese Patent Laid-Open No. 95447/1976 and Japanese Patent Laid-Open No. 9847/1978 the use of a .beta.-diketone compound or a metal salt thereof and a metal soap.
Although these .beta.-diketone compounds are effective in the improvement of coloration, they are less effective in the improvement of heat stability over a prolonged period of time.
Thus Japanese Patent Publication No. 6465/1982 has proposed to use a .beta.-diketone compound or a metal complex salt thereof together with an overbased alkali metal or alkaline earth metal organic sulfonate or phenolate complex to thereby simultaneously improve the heat stability and the coloration.
Recently, the use of halogenated resins have been diversified and thus the processing conditions and the environment of use therefor have become more and more severe, which makes the stabilizing effect of known stabilizers insufficient. Further, there has been frequently observed the use of a composite material comprising a halogenated resin and a different kind of material, for example, a metal. However a conventional compounding system has only a limited adhesiveness to a different kind of material and, as a result, readily peels off, which results in an additional disadvantage.
Thus it has been urgently required to find out a stabilizer system for a halogenated resin whereby not only the heat stability at a processing temperature and coloration of the halogenated resin but also the heat stability at a relatively high temperature of approximately 100.degree. C. (i.e., the so-called heat aging characteristics) and the adhesiveness to a different kind of material can be improved.